Etc (Electrical toll collection) is the most advanced road and Bridge toll collection in the world. Through the microwave special short-range communication between the on-board unit installed on the windshield of the vehicle and the roadside unit installed on the etc lane of the toll station, the computer networking technology is used to conduct background settlement processing with the bank, so as to achieve the purpose that the vehicle can pay the road and bridge fee through the Road and Bridge toll station without stopping.

This paper will focus on the on-board unit OBU equipment in ETC system and the ESAM unit in OBU equipment that records vehicle information and user information.

ETC system composition and working principle

The ETC system consists of a front-end system and a back-end database system. The overall architecture is shown in the following figure:


The front-end system consists of on board unit (OBU), roadside unit (RSU) and lane controller installed on the windshield. The overall architecture of the front-end application system is shown in the following figure:


Take the etc Lane in the form of automatic railing island layout mode as an example to introduce the principle of vehicle traffic. The automatic railing island layout mode is shown in the following figure:


When the vehicle enters the etc antenna communication area, the ground coil senses the arrival or departure of the vehicle and transmits the signal to the lane controller. The lane controller controls the RSU to establish a communication link with the OBU on the vehicle through the DSRC signal, complete the two-way authentication and entry / exit information writing, and upload the obtained relevant information such as vehicle ID number, vehicle model The license plate number and other information are compared and judged in the central management system and the corresponding information in the database, and the management system is controlled to produce different actions according to different situations. For example, the computer toll management system deducts the toll payable this time from the vehicle’s account, or sends instructions to other auxiliary facilities. Other auxiliary facilities, such as camera system for illegal vehicles, automatic control railings or other obstacles, and traffic display equipment (red, yellow, green lights, etc.) to instruct vehicles to drive.

OBU system composition

OBU is classified according to the type of user card, which can be divided into two-piece OBU and multi logic channel OBU. The user card of two-piece OBU is separated from ESAM, and a separate user card will be inserted into the OBU equipment; Multi logical channel is the combination of user card and ESAM into one ESAM by using multi logical channel synthesis technology. According to the installation stage, it can be divided into front mounted OBU and rear mounted OBU. The front mounted OBU means that the OBU has been installed before the vehicle leaves the factory, and the whole OBU needs to pass the vehicle specification Level certification; The rear mounted OBU is installed after the vehicle leaves the factory, and there is no restriction of vehicle specification Level certification. Although the OBU classification seems very complex, the overall architecture is not much different. The OBU architecture is roughly shown in the following figure (taking multi logical channel OBU as an example):


OBU consists of master MCU, esam/icc, RF, Bluetooth, power supply and some peripheral devices. The master MCU realizes the overall logic of OBU and provides the function of information forwarding from ESAM to RSU.

ESAM logic unit is a safety unit in essence, which stores vehicle information, release information and other data, which can be read and written under safety conditions.

The essence of ICC logic unit is an electronic wallet card, which is divided into account card and stored value card. The account card contains basic information such as user ID. users can use this card to keep accounts in the toll lane first, and their consumption amount will be deducted from the user’s prepaid account (prepayment method) or settled later (post payment method); The stored value card contains a certain amount of money that the user has pre deposited in the account. The card contains the user ID and stored value information. The user can use this card to pay directly in the toll lane. The consumption amount will be deducted from the card and from the user’s pre deposited account.

For two chip OBU, ESAM logic unit and ICC logic unit are two separate devices. For multi logic channel OBU, ESAM logic unit and ICC logic unit are synthesized into a multi logic channel ESAM device by using multi logic channel synthesis technology.

Shanghai Hangxin, multi logic channel ESAM

For the ETC system, Shanghai Hangxin has developed two multi logical channel obe-sam products, the models of which are acl16-s8a and acl16-s8b respectively. Acl16-s8a is a front mounted product and acl16-s8b is a rear mounted product. The main features of the product are as follows:

• the security chip adopts 32-bit CPU core

• support SM4 algorithm and TDES algorithm

• user area data storage capacity 32kbytes, 500000 erasures

• support iso/iec 7816 t=0 communication protocol

• the iso/iec 7816 interface clock is not higher than 15MHz and supports multiple baud rates (9.6kbps~223.2kbps when the external clock frequency is 3.57mhz)

• support multiple file types, including binary file, fixed length record file, variable length record file and circular file

• support multiple security access methods and permission management

• the product meets the technical requirements for toll road Networking Electronic Toll Collection

• the product complies with ESAM module safety assessment test

• the product complies with the physical characteristics test of the obe-sam module of networked electronic charging multi logical channel

• the security chip has reached the level of national secret level II certification

• security chip reaches eal5+ certification level

• comply with aec-q100grade1 test certification of vehicle specification level (only acl16-s8a)

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